The present invention relates to interworking of Internet Protocol (IP) and Universal Mobile Telecommunications Service (UMTS), and deals more particularly with translation between IP Quality of Service (QoS) parameters and UMTS QoS attributes.
With the advent of third generation radio access technology, conventional norms of mobile telephony will become a thing of the past. Mobile technology will now be able to offer features, such as multimedia and information services, that go far beyond basic telephony. A perpetually expanding consumer market for these services is being created by the widespread growth of the Internet. However, several challenges are anticipated in the event of providing these services. From a market perspective, this would involve merging the installed base of users in both cellular and Internet environments. Technologically speaking, the challenge would be to determine common denominators for cellular solutions on one hand, and efficient Internet access on the other. To successfully meet these challenges, the third-generation wireless systems must be designed to provide a multitude of services, provide considerable flexibility, and provide structured QoS handling and cost-effective access while ensuring coverage with high radio spectrum efficiency.
The Internet has traditionally operated on a “best effort” basis. Best effort service has been adequate for legacy data traffic and applications that can adapt to bandwidth and delay variations. However, in recent years, there has been a growing need for applications that require real-time and other QoS guarantees, to be able to run on the Internet. The advent of high-speed networks and processors has made possible a variety of widely distributed applications. However, the lack of real-time services and guarantees in the Internet domain has limited large-scale deployment of such applications. These applications have end-to-end QoS requirements that can be expressed in terms of their timing, and the precision and accuracy of the services they offer. For example, a typical user of a videoconference application is ultimately interested in the quality of the picture (the end result); however this is in turn an aggregation of the QoS of capturing the video, compressing it, transmitting it over the network, decompressing it, and finally displaying it.
Internet QoS can be expressed as the combination of network imposed delay, jitter, bandwidth and reliability. Delay is the elapsed time for a packet to traverse from a source to a destination. Jitter is the perceived variation in end-to-end delay. Bandwidth is the maximal data transfer rate that can be sustained between the source and the destination. Finally, the transmission is reliable if it delivers all the packets in the correct order, without dropping them or causing bit errors. Reliability is a property of the transmission system and is affected by the average error rate of the medium as well as by routing and switching designs. In the wireline Internet, packet loss is caused mainly by congestion. However, in wireless networks both congestion and the unreliability of media must be considered.
Various drawbacks of Internet QoS as stated above can be taken care of, to some extent, by offering diverse services rather than a single service that is the best effort service offered by the current Internet. Network services, such as Differentiated Services (Diffserv) and Integrated Services (Intserv) have been designed to offer multiple service levels.
Each of the abovementioned QoS provisioning services provides QoS using different paradigms. Diffserv and Intserv are proposed by the Internet Engineering Task Force (IETF), and built on the TCP/IP (Transmission Control Protocol/Internet Protocol) suite. Diffserv is a packet-based priority service deployed in intermediate systems such as routers, and provides Assured and Premium services with differentiated service priorities. Intserv is a flow-based reservation service deployed in both end (e.g., hosts) and intermediate (e.g., routers) systems, and provides Controlled-Load and Guaranteed services to applications like real-time communications.
Each QoS provisioning service serves applications by providing their own custom user interfaces; this includes Application Programming Interfaces (API) and QoS specifications. Diffserv uses the Bandwidth Broker (BB) and its API, and Intserv uses the Resource ReSerVation Protocol (RSVP) and its API (RAPI).
Applications therefore need to cope with the heterogeneity of user interfaces to ensure their QoS. In addition, the QoS requirements vary from application to application. For example, an Internet telephony application requires voice signals to arrive within a tolerated delay variance (jitter); a video player requires a bandwidth guarantee to convey the images smoothly (bandwidth); and a real-time monitor requires a strictly assured delay of communication (delay).
An important issue that arises now is the ease with which an application can interact with the QoS provisioning services. First, a user may not have exact knowledge of the specific service offered by the network, and may not know how to customize a QoS request for its needs. Second, network QoS may be expressed using different service models and bring about inconsistent resource utilization. Third, legacy applications need to be extended or assisted to access and control QoS delivery. Fourth, interworking of QoS control with systems and applications, which are not equipped to handle QoS, becomes especially important when QoS control is only partially available to some network systems. The problem is further magnified when a wireless system happens to be part of an IP end-to-end communication.
Of particular interest is the specific case where the wireless system is UMTS based. A detailed discussion on this case is carried out hereinafter.
FIG. 1 shows an IP network. The diagram shows two users, but could be easily adapted to include many more users without changing the basic functionality of the network.
In FIG. 1, User-A may communicate with User-B over a text-based or voice-based chat. Similarly, User-A may communicate with an application server that could be a video streaming server. The common component in both these accesses is that the users connect to the IP backbone network through local access networks such as a telephone, GSM (Global System for Mobile Communications), GPRS (General Packet Radio Service), or UMTS network. Moreover, this local access network could be different for User-A and User-B. The IP backbone network may have a number of routers to route packets between User-A and User-B, and between User-A and the application server.
As far as the users are concerned, it is the QoS perceived by them that matters. Hence all intermediary networks need to “cooperate” with each other and “understand” each other's QoS levels.
Different applications can access the network through various application programming interfaces (APIs). An API provides the application programmer with a uniform interface to access the underlying system resources. For example, if the IP network is a Diffserv network, an application program may request that all of its IP packets receive “Expedited Forwarding” treatment.
Note that the API may be oblivious to the technologies that are embedded in the various access networks and backbone networks, which in turn may employ their own QoS levels. For example, the user may use an RSVP/Intserv based API, whereas the end-to-end embodiment may include a UMTS access network and a non-RSVP enabled IP network. In such cases, certain mechanisms are required to make sure that QoS is provided end-to-end.
FIG. 2 shows an End-to-End Integrated Service between the hosts. The service is provided using routers and hosts that support the service definition through signalling of the relevant information between the nodes. The hosts use RSVP to request desired quality of services that they want from the network, for a particular application. All the intermediary routers also use RSVP to deliver QoS to every node all along the path, and to establish and maintain state in order to provide the requested service. A RSVP request will in general result in the network reserving resources at all the nodes on the way to the destination.
GPRS and UMTS may form a part of the overall network and play an important role in the end-to-end bearer service for the customers connected to it. Thus, the services provided over the GPRS/UMTS network must be suitable in aspects of control signaling and user plane transport so that it can provide the required end-to-end bearer service. FIG. 3 illustrates this specific case of FIG. 1 where the local access network is a GPRS/UMTS network. The GPRS/UMTS network consists of a set of network elements between the host, referred to as the Mobile Station (MS), and the external packet switching network that the user is connected to. The Serving GPRS Support Node (SGSN) provides mobility management and authentication for the corresponding MS. The Gateway GPRS Support Node (GGSN) acts as a gateway between the UMTS Core Network and external networks.
The bearer must be set all the way from the source to the destination of a QoS Bearer Service to realize clearly defined characteristics and functionality. To enable the provision of a contracted QoS, a bearer service must include all the requisite aspects. The QoS requirements depend on the current UMTS QoS class under consideration.
FIG. 4 illustrates the QoS classes for UMTS. There are four different QoS classes: Conversational class, Streaming class, Interactive class, and Background class. The main distinguishing factor between these QoS classes is their delay sensitivity: Conversational class is meant for delay sensitive traffic, whereas Background class is meant for traffic that is delay insensitive. Conversational and Streaming classes are mainly intended to carry real-time traffic. The main differentiator between them is their respective delay sensitivity. Conversational real-time services, like video telephony, are the most delay sensitive applications and these data streams should be carried in Conversational class.
The Interactive and the Background class are mainly intended to be used by traditional Internet applications like the World Wide Web (WWW), Email, Telnet, File Transfer Protocol (FTP) and News. Due to looser delay requirements, as compared to Conversational and Streaming classes, both provide better error handling by means of channel coding and retransmission. The main difference between Interactive and Background class is that Interactive class is mainly used by interactive applications, e.g. interactive Email or interactive Web browsing, while Background class is meant for background traffic, e.g. background download of Emails or background file downloading. Responsiveness of the interactive applications is ensured by separating interactive and background applications. Traffic in the Interactive class has higher priority in scheduling as compared to Background class traffic, so background applications use transmission resources only when interactive applications do not need them. This is very important in the wireless environment where bandwidth is scarce as compared to wired networks.
FIG. 5 provides an overview of the uses of different UMTS QoS attributes. The exact definitions of these attributes can be found in 3GPP TS 23.107.
In FIG. 6, the UMTS bearer attributes and their relevancy for each bearer traffic class are shown.
FIG. 7 provides an overview of some IP QoS parameters. IP QoS parameters have been divided into three classes: Controlled Load service parameters, MIME specific parameters and ‘wireless hints’ (proposed to IETF for standardization). MIME specific parameters and ‘wireless hints’ are considered as optional.
FIG. 8 depicts UMTS bearer service layered architecture. On its way from one Terminal Equipment (TE) to another, the traffic has to pass through different bearer services of the network(s). A TE is connected to the UMTS network by use of a Mobile Terminal (MT). The End-to-End Service on the application level uses the bearer service(s) of the underlying network(s). The End-to-End-Service used by the TE will be realized using a TE/MT Local Bearer Service, a UMTS Bearer Service, and an External Bearer Service. The UMTS Bearer Service is the bearer service that provides the UMTS QoS.
QoS management functions of the UMTS bearer service for the control plane and QoS management functions for end-to-end IP QoS are illustrated in FIG. 9. These are described in detail in 3GPP TS 23.107 and 3GPP TS 23.207.
The system as described above (i.e. UMTS as a part of IP end-to-end communication) will have a large variety of applications. As a result of such large variety of applications that UMTS is going to offer, it is speculated that IP-UMTS traffic will increase tremendously in future. Such applications would include video streaming, video conferencing, and Multimedia Messaging Services. This will create a need for efficient utilization of bandwidth, especially in the UMTS domain, as there is a paucity of bandwidth in the wireless medium. If one is able to translate IP QoS parameters to UMTS QoS attributes, one could easily determine the bandwidth requirement for the particular application, thereby resulting in efficient spectrum utilization.
Furthermore, applications will also be required to negotiate the services at different levels (e.g. kind of application and received QoS), for which translation between IP QoS parameters and UMTS QoS attributes seems to be an imperative. This translation is likely to result in more efficient service negotiation between an entity at the IP level and the entire UMTS network itself.
Certain patents have been filed in this area. International Patent Application No. WO 01/56250, titled “RSVP handling in 3G networks”, deals with providing a method in a mobile terminal to support RSVP signalling in 3G wireless networks. The mobile terminal is connected to local user's terminal equipment and is also in communication with the radio network. To support interworking of RSVP and IP QoS information in the UMTS network, the invention provides a method to include IP QoS information in a Packet Data Protocol (PDP) context, and to carry the QoS information through the UMTS network. However, it does not address the issue of translation of IP QoS parameters to UMTS QoS attributes and vice-versa, which is essential for efficient spectrum utilization in the UMTS domain while dealing with IP traffic. This translation function is also required for service negotiation between an entity at the IP level and the entire UMTS network.
This translation between IP QoS parameters and UMTS QoS attributes is not trivial because of several reasons. First, the number of QoS parameters at the two levels is different, because of which the mapping is not one-to-one. Second, the definitions of parameters at the two levels are different. This is true both for range and the expected usage of the parameters. This is e.g. due to different ways of providing QoS (over-provisioning in the IP networks of today versus spectrum efficient transport in cellular networks). Third, the problem of translating the IP QoS parameter set that includes the Wireless hints (specified in FIG. 7) has not been solved earlier.
Therefore, what is needed is a translation function for translation between IP QoS parameters and UMTS QoS attributes.